PID controller feedforward

Restructures the PID controller to decouple feedforward from D.

Cleaned up the structure of the PID controller; moved some feature-based enhancements out of the main structure.

Feedforward becomes a separate component of the PID controller and there is now:
f_pitch
f_roll
f_yaw

The default values of 60 for pitch and roll matches the default setpoint weight used in BF3.4.  Yaw previously had no setpoint weight capability so the default here needs to be discussed.  Currently it's also set to 60 and flight testing seems positive.  Feedforward on yaw adds a lot of value so I don't think we want to default to 0.  Instead we need decide on the default.

All occurences of setpoint weight have been replaced by feedforward. "setpoint_relax_ratio" has been renamed to "feedforward_transition".

The pidSum now consists of P + I + D + F.

D has been added back for yaw (disabled by default with d_yaw = 0). We've found little need for D for normal quads but it may have value for other configurations - particularly tricopters.

Updated CMS menus to support adjusting the feedforward for each axis.

Changed the default for "rc_interp_ch" to be "RPYT".  Need yaw to be smoothed to support feedforward.

Open issues:

Needs BFC support
- Need to add support for the axis "F" gains.
- Remove "setpoint weight" slider.
- Rename "D Setpoint transition" to "Feedforward transition"

Needs BBE support
- Header "setpoint_relaxation_ratio" has been renamed "feedforward_transition"
- Header "dterm_setpoint_weight" has been replaced with an array named "feed_forward_weight".
  example: H feed_forward_weight:65,60,60    (R,P,Y)
- PID component "AXISF" has been added for all axes. Should be handled like P, I and D values.
- PidSum calculation needs to include F.

Needs LUA script support
- Support the renamed "setpoint_relax_ratio".
- Support for feedforward weight on all 3 axes.

Open code issues:
- rc_adjustments.c - support for adjusting feedforward weight for all axes. Currently only supporting roll - needs coordination with BFC.

src/main/interface/msp.c

@@ -1293,8 +1293,8 @@ static bool mspProcessOutCommand(uint8_t cmdMSP, sbuf_t *dst)
         sbufWriteU16(dst, 0); // was pidProfile.yaw_p_limit
         sbufWriteU8(dst, 0); // reserved
         sbufWriteU8(dst, currentPidProfile->vbatPidCompensation);
-        sbufWriteU8(dst, currentPidProfile->setpointRelaxRatio);
-        sbufWriteU8(dst, MIN(currentPidProfile->dtermSetpointWeight, 255));
+        sbufWriteU8(dst, currentPidProfile->feedForwardTransition);
+        sbufWriteU8(dst, 0); // was low byte of currentPidProfile->dtermSetpointWeight
         sbufWriteU8(dst, 0); // reserved
         sbufWriteU8(dst, 0); // reserved
         sbufWriteU8(dst, 0); // reserved
@@ -1304,7 +1304,7 @@ static bool mspProcessOutCommand(uint8_t cmdMSP, sbuf_t *dst)
         sbufWriteU8(dst, 0); // was pidProfile.levelSensitivity
         sbufWriteU16(dst, currentPidProfile->itermThrottleThreshold);
         sbufWriteU16(dst, currentPidProfile->itermAcceleratorGain);
-        sbufWriteU16(dst, currentPidProfile->dtermSetpointWeight);
+        sbufWriteU16(dst, 0); // was currentPidProfile->dtermSetpointWeight
         sbufWriteU8(dst, currentPidProfile->iterm_rotation);
 #if defined(USE_SMART_FEEDFORWARD)
         sbufWriteU8(dst, currentPidProfile->smart_feedforward);
@@ -1333,6 +1333,9 @@ static bool mspProcessOutCommand(uint8_t cmdMSP, sbuf_t *dst)
 #else
         sbufWriteU8(dst, 0);
 #endif
+        sbufWriteU16(dst, currentPidProfile->pid[PID_ROLL].F);
+        sbufWriteU16(dst, currentPidProfile->pid[PID_PITCH].F);
+        sbufWriteU16(dst, currentPidProfile->pid[PID_YAW].F);
 
         break;
     case MSP_SENSOR_CONFIG:
@@ -1835,8 +1838,8 @@ static mspResult_e mspProcessInCommand(uint8_t cmdMSP, sbuf_t *src)
         sbufReadU16(src); // was pidProfile.yaw_p_limit
         sbufReadU8(src); // reserved
         currentPidProfile->vbatPidCompensation = sbufReadU8(src);
-        currentPidProfile->setpointRelaxRatio = sbufReadU8(src);
-        currentPidProfile->dtermSetpointWeight = sbufReadU8(src);
+        currentPidProfile->feedForwardTransition = sbufReadU8(src);
+        sbufReadU8(src); // was low byte of currentPidProfile->dtermSetpointWeight
         sbufReadU8(src); // reserved
         sbufReadU8(src); // reserved
         sbufReadU8(src); // reserved
@@ -1851,9 +1854,9 @@ static mspResult_e mspProcessInCommand(uint8_t cmdMSP, sbuf_t *src)
             currentPidProfile->itermAcceleratorGain = sbufReadU16(src);
         }
         if (sbufBytesRemaining(src) >= 2) {
-            currentPidProfile->dtermSetpointWeight = sbufReadU16(src);
+            sbufReadU16(src); // was currentPidProfile->dtermSetpointWeight
         }
-        if (sbufBytesRemaining(src) >= 7) {
+        if (sbufBytesRemaining(src) >= 13) {
             // Added in MSP API 1.40
             currentPidProfile->iterm_rotation = sbufReadU8(src);
 #if defined(USE_SMART_FEEDFORWARD)
@@ -1883,6 +1886,10 @@ static mspResult_e mspProcessInCommand(uint8_t cmdMSP, sbuf_t *src)
 #else
             sbufReadU8(src);
 #endif
+            // PID controller feedforward terms
+            currentPidProfile->pid[PID_ROLL].F = sbufReadU16(src);
+            currentPidProfile->pid[PID_PITCH].F = sbufReadU16(src);
+            currentPidProfile->pid[PID_YAW].F = sbufReadU16(src);
         }
         pidInitConfig(currentPidProfile);